1. Field of the Invention
The invention relates to a network coupling device and a network coupling system, more particularly to a network coupling device and a network coupling system that are to be used in a power over Ethernet (PoE) network.
2. Description of the Related Art
In a power over Ethernet (PoE) network, electrical power may be transmitted along with data on a single cable. For example, by using a cable with a register jack (RJ) 45 connector to interconnect a power source equipment (e.g., a network switch) and a power device (e.g., a wireless router, a webcam, a voice over Internet Protocol (VoIP) device, etc.), the power source equipment is able to transmit data and power simultaneously to the power device through the cable. The PoE network allows the power device to operate without having to be connected electrically to a power source (e.g., a household power outlet, a battery, etc.).
A conventional Ethernet transformer is typically installed in the power source equipment for handling transmission of data and power. As various power devices are configured to incorporate more functionalities, power consumptions of the various power devices are accordingly increased. As a result, the power source equipments are required to be able to transmit a larger amount of power. In order to meet the larger power requirement, an iron core of the Ethernet transformer must be made larger in size, and copper coils with larger diameters must be adopted for winding. However, such changes on the Ethernet transformer also change an inductance, and in turn, an equivalent impedance of the Ethernet transformer. In such a case, in order to achieve impedance matching, an equivalent impedance of the power source equipment must be redesigned as well.